The preparation of a mixture of the .alpha. and .beta. isomers of .alpha.-pivaloyloxyethyl-(S)-3-(3,4-dihydroxyphenyl)-2-methylalaninate (POE Ester) has been described by W. A. Saari, et al., Journal of Medicinal Chemistry, 21, 746 (1978) and U.S. Pat. No. 3,983,138 who also discloses a process for the resolution of this .alpha./.beta.-isomer mixture to obtain only the .alpha.-isomer in its pure state as the hydrochloride salt.